An official Path Through History Site! The first fortification to be located on the site of the current Fort Ontario was built by the British in 1755. Construction of a second British fort began in 1759, and the second fort was destroyed in 1778 by American troops stationed at Fort Stanwix. Between 1839 and 1844, the US Fort Ontario was built. Between 1944 and 1946, the Fort was used as a Holocaust refugee center, the only one of its kind in the country.